Also calledliquor purisor purulent exudate, it is produced as part of the body’s response to an infection.
Pus is usually odorless but can emit a foul odor if an infection is severe.
Surgeries or diseases like appendicitis or diverticulitis can also cause infections in deeper tissues that lead to pus.
Photo: Angela Palmer
Photo: Angela Palmer
How Does Pus Form?
Pus is a byproduct of your immune system’s fight against an invader, usually bacteria or certain fungi.
When an infection occurs, theimmune systemwill send different white blood cells (leukocytes) to fight it.
Verywell / Laura Porter
These includemacrophagesand dendritic cells that surround and absorb the invader, killing them through a process known asphagocytosis-induced apoptosis.
This is when white blood cells “commit suicide” to kill the invader they have absorbed.
Pus is usually an opaque, white-yellow color.
It can also be brown or green.
The accumulation of pus within an enclosed space in deeper tissues is known as anabscess.
What Does Pus Do?
Pus doesn’t serve any function.
It is simply the byproduct of the immune response.
With pustules, your body may be able to slowly absorb and break down the pus without treatment.
The pustule may also drain naturally, eventually shrinking and drying up.
There are steps you might take before and after any procedure to reduce your risk of an SSI.
The night before surgery, wash your whole body with soap in the bath or shower.
Do not shave near the surgical site.
It can irritate the skin and increase your risk of infection.
(If shaving is needed, the surgical staff will do it for you.)
Family or friends should wash their hands before visiting and should not touch your wound.
Always wash your hands before and after caring for the wound.
Inspect your incisiondaily for signs of infection.
Clear or blood-tinged drainage from a surgical wound is considered normal unless there is a large amount of it.
Wound drainage can last anywhere from one to five weeks, depending on the extensiveness of the procedure.
Treatment
If an infection causes pus, it more often than not requires treatment.
Your healthcare provider may collect a sample of pus and send it to a lab forcultureand sensitivity testing.
Topical antibiotics can also be used for superficial fungal infections, mainly to prevent asecondary infection.
This is when a fungal skin infection causes a break in the skin that allows bacteria to enter.
Fungal infections are directly treated withantifungals.
Drainage and Tissue Removal
In some cases, anabscess drainagemay be needed to clear pus.
In such cases, if pus is not cleared, the infection may be harder to resolve.
External abscesses may be lanced (cut) or drained with a needle and syringe.
A surgeon or interventional radiologist may drain an internal abscess.
The catheter time duration depends on the size and cause of the abscess.
It involves thoroughly cleaning the wound and removing anynecrotic(dead) or infected tissues along with any debris.
This is particularly important if you recently had surgery.
It can also put you at risk of serious and even life-threatening complications, such as sepsis.
Summary
Your body produces pus as a response to infection.
Pus is made up of dead white blood cells, bacteria or fungi, and tissue debris.
Pus can occur with common skin infections like acne or when bacteria enter hair follicles or cuts.
It can also develop in deeper tissues that are contaminated during surgery or by local or systemic infections.
Proper wound care can prevent pus from developing.
If an infection causes pus, treatment may include antibiotics, pus drainage, and possibly surgical debridement.
Icahn School of Medicine at Mount Sinai.Surgical wound infection - treatment.
St. Elizabeth’s Medical Center.Abscess drainage.
New York State Department of Health.Bacterial skin infections: Impetigo and MRSA.
Centers for Disease Control and Prevention.Surgical site infections (SSIs).
2022:S0104-0014(22)00074-4. doi:10.1016/j.bjane.2022.06.002
Johns Hopkins Medicine.Urinary tract infections.
Centers for Disease Control and Prevention.FAQs: About surgical site infections.
